Method and apparatus for manipulation of a load for cleaning tower structure components

ABSTRACT

For controllably suspending a load from a helicopter such that the load can be quickly jettisoned in an emergency, a rigid stabilizer bar is suspended from a quick-release cargo hook attachment point of the helicopter, and a yoke structure is releasably carried by the hook in fixed relation to the bar, opposite ends of the yoke having flexible lines connected to spaced apart locations on the load. Opposite ends of the stabilizer bar are connected by bungee cords to landing skid anchors for stabilizing the yoke. The attitude of the load is controlled by yawing and rolling maneuvers of the helicopter. If necessary, the yoke, together with the lines and the load, can be jettisoned from the vehicle by releasing the hook. The load can be configured as a cleaning module for directing a cleaning medium onto an elevated workpiece such as an insulator of a transmission line tower. The cleaning module produces a stream of particulate such as crushed walnut shells in a high-pressure air blast from a nozzle that is located on a boom projecting from the module, the nozzle being aligned in a predetermined direction relative to the yoke. The helicopter can fly with the cleaning module suspended beside the insulator, the nozzle being aimed relative to the workpiece horizontally by yawing the helicopter and vertically by rolling the helicopter, the module having a first position proximate the helicopter, and a second lower position for use with single circuit towers having three horizontally displaced insulators.

This is a division, of the application Ser. No. 177,589, filed Apr. 4,1988 now U.S. Pat. No. 4,973,361 issued Nov. 27, 1990.

BACKGROUND

The present invention relates to maintenance of elevated structures, andmore particularly to the controlled manipulation of a load in connectionwith such maintenance, for cleaning components of the structures.

The manipulation of loads in connection with tower structureconstruction and maintenance is a key to the viability of suchstructures. For example, some important structures have been erected atremote and foreboding sites only because it has been possible to fly thecomponents to each site by helicopter, the parts being attached to eachstructure while the helicopter hovers with the load properly positionedand oriented. See, for example, U.S. Pat. No. 4,378,919 to H. Smith thatdiscloses apparatus by which a load suspended from a helicopter is freeto swing beneath the helicopter, yet the rotational position of the loadabout a vertical axis is controlled by yaw manipulation of thehelicopter. The Smith disclosure includes a yoke by which the load issuspended on a pair of cables, the yoke being restrained from rotationunder the helicopter by a ring-shaped tubular structure that forms apair of slots for receiving opposite ends of the yoke. A linkage allowsthe tubular structure to move back and forth in response to swinging ofthe cargo hook.

The Smith device is subject to several disadvantages. For example, thelinkage is somewhat complex, having several swinging joints. Also, theslot in the tubular structure must provide extra clearance for the yoketo allow for lateral tipping of the tubular structure, reducing theeffectiveness of the structure in yaw control. Further, anchor pointsfor the linkage must be provided on the aircraft structure. Moreover,there are times when further control of a suspended load beyond mererotational control is needed. For example, in one aspect of towerstructure maintenance, it is desired to clean critical portions of thestructure, such as insulators of high voltage power transmission towers.

Presently, the insulators are cleaned at relatively long range usingdeionized water at high pressure. This can be done from the ground usingwhat amounts to a fire truck, and a man carrying a hose can also climbthe tower. Attempts to do this from the air have had limited successbecause water is too heavy for economical transport by helicopter, and asecond crew member is required for operating a nozzle turret that isneeded for directing the stream sufficiently accurately. This greatlyincreases the of weight to the load, and the hardware is expensive. Theexpense of the hardware is aggravated by the need for of FAAcertification. See, for example, U.S. Pat. No. 4,090,567 to Tomlinsonthat discloses a fire fighting helicopter, and U.S. Pat. No. 4,477,239to Kurtgis that discloses a tower insulator cleaning apparatus that iscarried by helicopter. Also, when the helicopter is large enough forcarrying a meaningful load, two pilots are required under FAAregulations.

Water creates its own problems in that when it is contaminated by dirtfrom the insulator, it becomes conductive, creating a danger of arcing.Moreover, there are large reactive forces to contend with. "Drycleaning" has also been done using a blast of air and particles ofwalnut shells, sand, corn husks or the like. But the air blast has ashort range of only two or three feet, tending to preclude effectivecleaning from a nozzle mounted on the helicopter, which must fly closeto the wires. Also, when hoses are used, such as by a man climbing thetower, the losses are prohibitive.

As mentioned above, a disadvantage of the Kurtgis apparatus is that atleast two crew members are required, and only a relatively smallquantity of the liquid spray can be carried. Also, the helicopter mustfly at a low altitude approximately corresponding to the height of eachinsulator to be cleaned. This presents the danger that a gust of wind orother emergency might cause the helicopter to crash into the towerand/or the transmission lines, with disastrous consequences. Moreover,the center insulator on a conventional "single circuit" tower is nearlyinaccessible from the side, and must be cleaned at long range.

A further disadvantage of the Kurtgis apparatus is that the nozzle islocated at the end of a long boom for clearing the ends of the rotorblades. This makes the nozzle particularly difficult to aim accurately.This difficulty is aggravated by the independent control of the positionand orientation of the helicopter by its pilot, and the separate aimingof the nozzle in both yaw and elevation by the boom operator. Moreover,the nozzle and/or the boom can get caught in the tower, with theconsequent likelihood of crashing the helicopter because neither theboom with its nozzle, nor the remainder of the heavy cleaning apparatusand its operator can be released in an emergency.

Thus there is a need for a highly mobile apparatus with which tomanipulate a load, such as in dispensing a cleaning medium, accuratelyin both yaw and elevation. Also, there is a need for such apparatus thatis safe to operate in close proximity to high voltage power transmissionlines and towers. There is a further need that such apparatus be adaptedfor effectively and rapidly cleaning large numbers of tower components,and be inexpensive to build and easy to operate.

SUMMARY

The present invention meets these needs by providing an apparatus andmethod for controllably suspending a load from a hoverable vehicle suchthat the load can be quickly jettisoned in an emergency. In one aspectof the invention, the apparatus includes a rigid stabilizer bar that issuspended from a quick-release cargo hook attachment point of thevehicle, a yoke structure releasably carried by the hock, opposite endsof the yoke being adapted for lifting the load by respectiveload-carrying lines, the yoke structure being removably held in fixedrelation to the bar while the yoke structure remains suspended by thehook, and biasing means for yieldably holding the stabilizer bar fixedabout a vertical axis and at least one horizontal axis relative to thevehicle. In an emergency the hook can released so that the yoke,together with the lines and the load, may be jettisoned from thevehicle.

The structural members can be located on opposite sides of alongitudinal axis of the vehicle, the horizontal axis of the biasingmeans preferably corresponding to the longitudinal axis for couplingroll motion of the vehicle to the load. Thus the present inventionadvantageously utilizes the roll attitude of the vehicle for controllingthe attitude of the load about a horizontal axis, the vehicle typicallyhaving greater maneuverability in roll than in pitch. A furtheradvantage of the present invention is that the combination of the rollcoupling and the suspension of the load below the vehicle creates apendulum effect that enhances the stability of the vehicle and the load.The structural members can be landing gear components of the vehicle,the apparatus including means for defining an anchor point on thosecomponents, the biasing means connecting the bar attachment points tothe anchor points. Further, the biasing means can include a pair ofextendable members connected between the bar attachment points and therespective anchor points.

Preferably the biasing means produces a greater stiffness about thelongitudinal axis than a lateral axis of the vehicle for permitting thevehicle to pitch relative to the load. Preferably the stiffness aboutthe longitudinal axis is at least about ten times that about the lateralaxis. More preferably, the stiffness about the longitudinal axis isbetween about ten and about fifty times that about the lateral axis. Forthis purpose, the anchor points can be spaced apart horizontally, thebar attachment points being located in a vertical anchor plane thatintersects the anchor points. Also, the attachment points can define abar axis that proximately intersects the attachment member. Further, thebar axis can be located vertically above the anchor points. Theextendable members can extend downwardly and laterally outwardly fromthe attachment points.

Preferably each of the anchor points can include a pair of anchormembers that can be spaced apart on opposite sides of the anchor planefor enhancing the stability about the vertical axis, an extendablemember being connected to each anchor member. Also, the anchor memberscan be movable to proximate the anchor plane for facilitating connectionof the extendable members. Moreover, the extendable members can includea bungee cord.

Another aspect of the invention provides a method for controllablysuspending a load from a hoverable vehicle, the vehicle having a loadattachment point, a releasable hook being connected thereto, and a pairof structural members fixably located on opposite sides of theattachment point, the method comprising the steps of:

(a) connecting a rigid stabilizer bar to the attachment point, thestabilizer bar extending on opposite sides of the attachment point torespective first and second bar attachment points;

(b) biasingly connecting the first and second bar attachment points torespectively to the structural members;

(c) connecting a yoke member to the releasable hook, the yoke fixablyengaging the stabilizer bar;

(d) connecting a pair of flexible tension members at one end thereof toopposite ends of the yoke member; and

(e) connecting opposite ends of the load to respective opposite ends ofthe tension members.

In a further aspect, the invention provides apparatus for cleaning anelevated workpiece from the hoverable vehicle, the apparatus includingmeans for defining a base, means for attaching the base below the hookmember, air compressor means attached to the base, tank means on thebase for holding a particulate solid material, the tank means beingconnected to and pressurized by the air compressor means, nozzle meansoperatively connected to the tank means for producing a stream of theparticulate material in response to air pressure in the tank means, andboom means for locating the nozzle in a predetermined position andorientation with respect to the base, whereby the stream of particulatematerial can be aimed relative to the workpiece horizontally by yawingthe vehicle, and vertically by rotating the vehicle about a horizontalaxis. The means for attaching the base below the hook member can includethe stabilizer bar, the biasing means for yieldably holding thestabilizer bar, the yoke member, and means for suspending the base fromthe yoke member. The means for suspending can be tension membersconnected from opposite ends of the yoke to spaced apart locations onthe base. The horizontal axis is preferably a longitudinal axis of thevehicle for vertically adjusting the stream by controlling the rollattitude of the vehicle.

The attachment means can include register means rigidly connected to thebase and being adapted for engaging a structural element of the vehicle,and a hook engagement member attached to the base for engagement by thehook. The combination of the hook engagement member and the registrationmeans provides at least a yieldably fixed location of the base relativeto the vehicle. The registration means can itself be capable ofpreventing rotation of the base about a vertical axis relative to thevehicle. For this purpose, the registration means can include anupwardly facing horizontally extending trough member for receiving anelongated cylindrical portion of the vehicle structural member that isoff set to one side of the hook and extends parallel to a horizontalaxis of the vehicle. Preferably the attachment means is capable ofholding the base at least yieldably fixed in a first position proximatethe vehicle, and a second position at least about six feet lower thanthe first position. The first position is particularly advantageous forcleaning dual circuit towers having three vertically spaced insulatorson each side; the second position provides convenient access forcleaning the center insulator of a single circuit tower having theinsulators spaced horizontally, in which case the vehicle flies abovethe tower with the module suspended proximate the center transmissionline. For this purpose, the attachment means can further include thestabilizer bar, yoke member, biasing means, and means for suspending thebase from the yoke member in the second position.

The apparatus can further include means for controlling the air pressurein the tank for controlling the rate of particulate material in thenozzle means.

The present invention, moreover, includes a method for cleaning aworkpiece, the workpiece being located at an elevation above groundlevel as a tower structure component, the method comprising:

(a) suspending a cleaning module from an airborne hoverable vehicle, themodule comprising:

(i) means for defining a base;

(ii) air compressor means attached to the base means;

(iii) tank means for holding a particulate solid material, the tankbeing connected to and pressurized by the air compressor means;

(iv) nozzle means connected to the tank means whereby a stream of theparticulate material is produced therefrom in response to air pressurein the tank means;

(v) boom means for locating the nozzle in a predetermined position andorientation with respect to the base means;

(b) maneuvering the vehicle for positioning the module proximate thetower structure with the nozzle having a positional elevation proximatethe elevation of the workpiece;

(c) yawing the vehicle for directing the stream laterally onto the workpiece; and

(d) rotating the vehicle about a horizontal axis for adjusting thestream vertically on the workpiece.

The step of rotating the vehicle about the horizontal axis can includerolling the vehicle about a longitudinal axis. Also, the method caninclude the further step of controlling the air pressure in the tankmeans for controlling the rate of particulate flow through the nozzlemeans. For this purpose, the method can include the further step ofcontrolling a source of power for the air compressor. The power can becontrolled between a first high level for producing the stream and asecond low level for preventing the stream. Moreover, the apparatus canfurther include a control valve between the tank means and the nozzlemeans, the method further comprising the step of operating the controlvalve for preventing the flow of the particulate material.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 is a front fragmentary sectional elevational view of a helicopterequipped with apparatus according to the present invention;

FIG. 2 is a side fragmentary sectional elevational view of the apparatusof FIG. 1;

FIG. 3 is a functional schematic diagram of the apparatus of FIG. 1;

FIG. 4 is a functional schematic diagram of an alternative configurationof the apparatus of FIG. 1 within region 4 of FIG. 3;

FIG. 5 is a front oblique elevational perspective view of the apparatusof FIG. 1 in use cleaning a first elevated workpiece;

FIG. 6 is an elevational perspective detail view of the apparatus ofFIG. 1 within region 6 of FIG. 5;

FIG. 7 is a fragmentary front elevational view of the apparatus of FIG.1 in an alternative configuration in use cleaning a second elevatedworkpiece;

FIG. 8 is a fragmentary front elevational view showing an alternativeconfiguration of the apparatus of FIG. 1 within region 8 of FIG. 7; and

FIG. 9 is a fragmentary detail elevational view of the apparatus of FIG.1 within region 9 of FIG. 2.

DESCRIPTION

The present invention is directed to an apparatus and method forcontrollably positioning a load from a hoverable vehicle, and further tothe application of the load in the form of a particulate medium to anelevated workpiece for the purpose of cleaning same. With reference tothe drawings, particularly FIGS. 1-3 and 5, a helicopter or otherhoverable vehicle 10 is equipped with a releasable cargo hook 12, thehook 12 being connected by an attachment bolt 14 to a cable 16, thecable 16 being attached to the vehicle 10 for suspending the hook 12underneath the vehicle 10. The vehicle 10 is also equipped with landinggear structure in the form of a pair of skids 18, the skids 18 beinglocated on opposite sides of a longitudinal axis 20 of the vehicle 10,the longitudinal axis 20 intersecting the hook 12. As shown in FIG. 1,the skids 18 are spaced apart by a distance S, the attachment bolt 14being located midway therebetween and elevated therefrom vertically by adistance H.

According to the present invention, an apparatus 30 for manipulation ofa load 32 includes a stabilizer unit 34 that is suspended from the hook12 and the attachment bolt 14 as described herein. The stabilizer unit34 includes a stabilizer bar 36 that extends horizontally on oppositesides of the hook 12 to respective bar attachment points 38, the barattachment points 38 being spaced apart by a distance X and displacedbelow the attachment bolt 14 by a vertical distance C. Each of the barattachment points 38 is biasingly connected to a respective skid 18 ofthe vehicle 10 by a corresponding bungee means 40, the connection ofeach bungee means 40 to the skid 18 defining an anchor point 42, theanchor point 42 being fixed relative to the respective skid 18. A yokeassembly 44 is suspended from the hook 12, the yoke assembly 44including a yoke truss 46 that extends on opposite sides of the hook 12to a pair of yoke attachment points 48, the yoke truss 46 beingreleasably connected to the hook 12 by an eye bolt 50, the yokeattachment points 48 being spaced apart by a horizontal distance Y andlocated a vertical distance D below the bar attachment points 38.

The yoke assembly 44 is held in a fixed position relative to thestabilizer bar 36 by means of spaced apart pairs of leg members 52, eachpair of the leg members 52 fixably depending from the stabilizer bar 36from proximate a respective bar attachment point 38, the leg members 52slidably engaging opposite sides of the yoke truss 46. A pair of cushionmembers 54 enclose the stabilizer bar 36, each of the cushion members 54being located proximate a pair of the leg members 52 for bearing againstthe top of the yoke truss 46 when the eye bolt 50 engages the hook 12. Adesired degree of pressure can be maintained between the cushion members54 and the top of the yoke truss 46 by appropriately adjusting the eyebolt 50. The attachment bolt 14, the eye bolt 50, the bar attachmentpoints 38, and the yoke attachment points 48 each lie in a common anchorplane, designated stabilizer plane 56 in FIG. 2. The stabilizer plane 56is nominally a vertical plane that is normal to the longitudinal axis 20of the vehicle 10, the bungee means 40 and the anchor points 42 alsobeing nominally located in the stabilizer plane 56.

The load 32 is suspended from the yoke assembly 44 by a pair of flexibletension members 58, each tension member 58 being connected between oneof the yoke attachment points 48 and a respective load attachment point60 of the load 32, the load attachment points 60 being spaced aparthorizontally by a load attachment distance 1;, the distance W beingapproximately equal to the yoke attachment distance Y between the yokeattachment points 48. The distance Y is less than the distance S, andthe distance C plus the distance D is less than the distance H forlocating the stabilizer unit 34 above ground level when the vehicle 10is at rest, and for permitting the tension member 58 to pass between theskids 18. Suitable tensioning of the bungee means 40 provides a highdegree of yaw stiffness of the stabilizer unit 34 about a vertical axis62 of the vehicle 10, the vertical axis 62 intersecting the attachmentbolt 14 and, nominally, the eye bolt 50. The distance X is preferablyfrom about 50% to about 90% of the distance S between the skids 18 forenhancing the yaw stiffness. More preferably, the distance X is betweenapproximately 65% and approximately 75% of the distance S. Also, thedistance C by which the bar attachment points 38 are displaced below thebolt 14 assures that when the stabilizer unit 34 is unloaded, thestabilizer unit 34 is effectively prevented from flopping around, thestabilizer plane 56 remaining approximately vertical. On the other hand,the distance C is made relatively small compared with the verticaldistance H by which the bolt 14 is located above the skid 18 forlimiting bending stresses on the stabilizer unit 34 in a horizontaldirection when the vehicle 10 rotates in pitch relative to the load 32.Accordingly, the distance C is made from about 20% to about 40% of thedistance H, being more preferably about 30% of the distance H. Also, anangle A is formed in the stabilizer plane 56 between each bungee means40 and the anchor points 42, the angle A being approximately 45°.

As shown in FIG. 2, each of the anchor points 42 has two counterparts,designated anchor band 43, that are spaced apart on opposite sides ofthe stabilizer plane 56, each being formed as a band member thatencloses the skid 18, and connecting a respective bungee means 40.Removable spacer means 66 are interposed between the bands 43 on eachskid 18. This arrangement advantageously permits the bungee means 40 tobe connected at reduced tension for ease of installation, and enhancesthe yaw stability of the stabilizer unit 34 for a given roll stiffnessthereof.

The combination of the roll coupling between the load 32 and the vehicle10 with the location of the load beneath the vehicle advantageouslyenhances the stability of both the vehicle and the load. This is becausethe combined mass of the load and the vehicle is centered further belowthe center of thrust than is the case when the load is within thevehicle.

An important aspect of the present invention is that the load 32 can bea cleaning module 70, the cleaning module 70 being particularly usefulin the maintenance of transmission line towers such as the tower 72shown in FIG. 5. The tower 72 serves to support a plurality oftransmission lines 74, each by a respective insulator or workpiece 76,the workpiece 76 requiring periodic cleaning maintenance for removingaccumulations of foreign material that would otherwise eventuallyproduce harmful arcing between the lines 74 and the tower 72. In FIG. 5,the tower 72 supports three of the transmission lines 74 in a typical"single circuit" three-phase configuration, the respective workpieces 76being horizontally disposed. Also, a pair of grounded sky lines 75 aresupported from the top of the tower 72 for preventing circuit damagefrom lightning.

The cleaning module 70 includes a frame or base 78 having an overheadload beam 80, the load beam 80 incorporating the load attachment points60. With further reference to FIG. 3, a tank 82 is mounted on the base78 for carrying the cleaning medium in the form of a particulate solidmaterial 84, a control valve 86 being connected to a bottom outlet 88 ofthe tank 82 for dispensing the material 84 through a delivery line 90.The delivery line 90 is connected to the control valve 86 by a Teefitting 92, and also to a nozzle 94, the nozzle 94 being mounted in apredetermined position and orientation with respect to the base 78 on aboom assembly 96. An air compressor means 98 is connected to the tank 82by a tank fitting 100, a manifold line 102 also connecting the tankfitting 100 to the Tee fitting 92. Thus the compressor means 98simultaneously pressurizes the tank 82 while delivering a large quantityof air at the same pressure to the delivery line 90. The tank fitting100 is also operatively connected through a solenoid valve 101 to thecontrol valve 86 for automatically opening the control valve 86 when thepressure at the tank fitting 100 reaches a predetermined level. Thuswhenever the pressure at the tank fitting 100 is at or above thepredetermined level, the material 84 is allowed to pass through thecontrol valve 86 at a predetermined rate for mixing with the air in thedelivery line 90 as long as the solenoid valve is also activated, thematerial 84 being ejected from the nozzle 94 with the air in ahigh-velocity stream 104.

In an exemplary configuration of the air compressor means 98, a screwcompressor unit 106 is operatively connected to a gasoline reciprocatingengine 108 by drive belt means 110, the engine 108 being fed by a fuelsupply 109. The compressor unit 106 includes a quasi-positivedisplacement twin-screw pump 112 having an air inlet 114, an oilcirculation system having a sump 115 and pump means 116, an air/oilseparator 117, a fan cooler 118, and an outlet 120, the outlet 120 beingconnected to the tank fitting 100. A compressor unit suitable for use asthe compressor unit 106 in the present invention is available as RotoModel 2A, Roto being a trademark of Bauer Compressors Inc., of Norfolk,Va. The Roto 2A compressor is capable of delivering over 120 cfm of airat 100 psi compressor discharge pressure when driven with a power inputof 30 horsepower. The compressor operates with essentially positivedisplacement between 4000 rpm and a service maximum about 6000 rpm,there being no effective seal below 3000 rpm such that a negligibleamount of power is required under idling conditions. The air flow rateranges from about 75 cfm at 4500 rpm up to about 130 cfm at the maximumof 6000 rpm.

An engine suitable for use as the engine 108 in the present invention isavailable as Rotax Model 503 from California Power Systems of San Jose,Calif. In a single carburetor version, this engine is capable ofdelivering approximately 25 horsepower at 4000 rpm, 30 horsepower at4500 rpm, 35 horsepower at 5000 rpm, 40 horsepower at 5500 rpm, and 44horsepower at 6000 rpm. This engine, which weighs approximately 70pounds, requires approximately 2.5 gallons per hour of fuel whenproducing 30 horsepower.

A torque converter unit 122 is connected between the compressor unit 106and the drive belt means 110 for enhancing the ability of the engine 108to deliver needed power to the pump 112 over a wide range of operatingconditions. Alternatively, the drive belt means 110 produces a 1:1 driveratio such that the speed of the engine 108 is the same as that of thepump 112. In fact, the engine 108 could be directly coupled to the pump112, except that one of the engine 108 and pump 112 would be required tobe configured for running in an opposite direction to that of thereadily available models of these components noted above.

As further shown in FIG. 3, the cleaning module 70 is controlled by anair control switch 124 which is located within the vehicle 10, theswitch 124 being operatively connected to a solenoid actuator 126 forcontrolling a throttle member 128 of the engine 108. When the solenoidactuator 126 is activated by the air control switch 124, the throttlemember 128 is moved to an adjustable substantially open position forproducing a predetermined high power output from the engine 108. Whenthe solenoid actuator 126 is deactivated, the throttle member 128 movesto an idle position for operating the engine 108 in an idling condition,the idling condition being at a speed substantially below 3000 rpm, suchas 1000 rpm. A media switch 129 for controlling the solenoid valve 101is also located within the vehicle 10. Accordingly, when the solenoidactuator 126 is de-energized, there is substantially no flow of eitherair or the material 84 from the nozzle 94, the control valve 86 beingclosed in response to low air pressure at the tank fitting 100. When thesolenoid actuator 126 is activated, high air pressure is obtained at thetank fitting 100, but the control valve 86 remains closed until thesolenoid valve 101 is activated by the media switch 129, at which timethe control valve 86 is opened and operational quantities of thematerial 84 are driven through the nozzle 94 with the air for producingthe stream 104.

A nozzle suitable for use as the nozzle 94 is available as Super Blastmodel DCV-4 from Empire Abrasive Equipment Corp. of Langhorne, Pa. TheDCV-4 nozzle includes a centered carbide venturi having a 0.25 inch ID,and is rated an air flow rate of 81 CFM and 494 pounds of sand flow perhour at a nozzle pressure of 100 psi, 18 horsepower being required.Other components appropriate for use as the tank 82, the control valve86, the delivery line 90, the Tee fitting 92, and the tank fitting 100,and the manifold line 102, are similarly available from Empire AbrasiveEquipment Corporation.

The boom assembly 96 includes an A-frame member 130, opposite legsthereof being pivotably joined by a pair of frame joints 132 to the base78, an arm member 134 being pivotably connected to the apex of theA-frame member 130 by an arm joint 136. The nozzle 94 is pivotablymounted to the arm member 134 remotely from the arm joint 136 by anozzle joint 138. Arm member 134 is fabricated from an electricallynon-conductive material for isolating the nozzle 94 from the A-framemember 130 and the base 78 of the cleaning module 70. Similarly, thedelivery line 90 comprises an electrically non-conductive material suchas rubber. As shown in the drawings, the arm member 134 is fabricatedfrom a tube of fiberglass, the delivery line 90 being supportivelylocated therein. The boom assembly 96 can extend from the base 78 adistance L between frame joint 132 and the arm joint 136, plus adistance M between the arm joint 136 and the nozzle joint 138, plus adistance N between the nozzle joint 138 and the end of the nozzle 92.The distance L can be about 7 feet, the distance M can be from about 3feet to about 7 feet, and the distance N can be about 8 inches. Thus themaximum distance between the frame joint 132 and the end of the nozzle92 is from about 11 feet to about 15 feet. The arm joint 136 and thenozzle joint 138 are fixably adjustable to predetermined relativeorientations. For this purpose, the arm joint 136 is provided with anadjustable arm joint clamp 140, and an adjustable nozzle joint clamp142. A flexible arm tension member 144 is connected to the boom assembly96 proximate the arm joint 136 and anchored to the base 78 proximate theload beam 80, the tension member 144 being equipped with adjustmentmeans 146 for adjustably defining an angle B of the A-frame member 130relative to the base 78, except that the tension member 144 permits theA-frame member 130 to be pivoted upwardly about the frame joint 132 toproximately a horizontal position when the cleaning module 70 is at reston the ground. Typically the tension member 144 is adjusted formaintaining the angle B between about 45° and about 60° for enhancing avertical distance Z between the nozzle 92 and a rotor 22 of the vehicle10, and for permitting the boom assembly 96 to clear obstructionsassociated with the tower 72.

In operation, the air switch 124 and the media switch 129 are bothswitched off until the vehicle 10, together with the cleaning module 70,approaches a tower 72 at which cleaning is to be done. Preferably, theair switch 124 is next turned on, activating the solenoid 126 forproducing the high-pressure output of the compressor means 98 asdescribed above. As the vehicle 10 is further maneuvered for bringingthe nozzle 94 proximate the workpiece 76, the solenoid valve 101 is thenactivated by the media switch 129 for producing the stream 104 as alsodescribed above. Normally, the solenoid 126 is energized continuouslywhile a full complement of the workpieces 76 of the tower 72 arecleaned. When it is desired to interrupt the stream 104 such as whenmoving between the workpieces 76, the media switch 129 is operated forde-energizing the solenoid valve 101. This is because the control valve86 responds relatively rapidly to operation of the solenoid valve 101 ascompared with operation of the solenoid 126, because of the timerequired for the engine 108 to change speeds, and for a correspondingchange of air pressure in the tank 82. When the last workpiece 76 of thetower 72 has been cleaned, the solenoid 126 is deactivated by operationof the air switch 124, with a consequent savings of fuel expended fromthe fuel supply 109 during transit to the next tower 72.

An experimental prototype of the cleaning module 70 as described above,but without the arm joint 136, has been built and tested, the module 70having a weight of approximately 550 pounds, the tank 82 being capablecarrying approximately 150 pounds of the material 84. The tests showthat prototype is operable to produce the stream 104 continuously forabout 45 minutes. It is expected that by substituting slightly largercounterparts of the tank 82 and the fuel supply 109, along with a modestweight-reduction of the module 70, continuous operation for one hour ormore will be possible.

It has been determined that the cleaning module 70 is effective incleaning the workpiece 76 with the nozzle 94 positioned at an operatingdistance O from the workpiece, the distance O being up to about 6 feet.Typically the workpiece 76 is an elongated cylindrical insulator 150having a spaced plurality of ring portions 152, as shown in FIG. 6. Ithas unexpectedly been discovered that by directing the stream 104upwardly and laterally against the ring portions 152, the material 84 isdeflected by the ring portions 152 such that substantially all of theinsulator 150 can be cleaned while the nozzle 94 is positioned to oneside only of the insulator 150, as shown in FIG. 6.

With further reference to FIG. 4, an alternative configuration of thecompressor means 98 includes a gas turbine compressor 161 and a coolermodule 163, the compressor 161 being provided with a fuel control 165that is responsive to the control switch 124. In this configuration, thecleaning module is capable of carrying a much larger payload because theweight efficiency of the compressor 161 is greatly improved over that ofthe compressor unit 106 and the separate engine 108.

In another important aspect of the present invention, the cleaningmodule 70 can be releasably carried proximate the vehicle 10 as analternative to the vertically separated configuration that is shown inFIG. 5. As shown in FIGS. 1 and 2, and with further reference to FIG. 7,the load beam 80 of the base 78 is equipped with a hook catch 160 forengagement by the releasable hook 12, the hook 12 also being capable ofclosing and latching about the catch 160. The vehicle 10 is alsoequipped with a winch means 162 for vertically positioning the hook 12as desired by the operator. An upwardly facing trough member 164 isrigidly attached to the load beam 80 for engaging one of the skids 18 ofthe vehicle 10. Thus with the stabilizer unit 34 removed, the vehicle 10can be made to hover above the cleaning module 70, the skid 18 beingguided into engagement with the trough member 164; and the hook 12,initially in its released condition, is engaged with the hook catch 160.As shown in FIG. 7, a mirror 166 is provided on the vehicle 10 forestablishing a line of sight 168 between the operator and the troughmember 164, the trough member 164 being located on an opposite side ofthe vehicle 10 from the operator. This is because the hook catch 160 islocated laterally slightly to one side of a center of gravity 170 of thecleaning module 70 for producing an upward force reaction at the troughmember 164 that maintains the engagement with the skid 18. It ispreferred that the trough member 164 be located opposite the boomassembly 96 because the lateral offset of the hook catch 160 results inan increased extension of the boom assembly 96 beyond the rotor 22 ofthe vehicle 10, the boom assembly 96 being located on the same side ofthe vehicle 10 as the operator for facilitating effective aiming of thenozzle 94.

In this alternative configuration, the cleaning module 70 is essentiallyrigidly coupled proximate the vehicle 10, the vertical distance Zbetween the nozzle 94 and the rotor 22 being substantially reduced by atleast about six feet compared with the previously describedconfiguration shown in FIG. 5. This alternative configuration is wellsuited for cleaning the insulators 150 of a "dual circuit" three phasetransmission tower 172 as schematically depicted in FIG. 7. As furthershown in FIG. 7, the nozzle 94 protrudes a distance P laterally beyondthe rotor 22 of the vehicle 10. Typically, the rotor 22 can have aradius R of approximately 13.2 feet. In an exemplary configuration ofthe present invention, the distance P is preferably between about 7 feetand 8 feet.

With further reference to FIG. 8, another alternative configuration isprovided by having two of the trough members 164 at opposite ends of theload beam 80, each of the trough members 164 engaging a respective skid18. In this configuration, the hook catch 160 is centrally locatedbetween the load attachment points 60, and between the trough members164. The mirror 166 is not required in this configuration because theline of sight 168 can be between the operator and the trough member 164on the same side of the vehicle 10. Suitable precautions, however, mustbe taken to prevent the winch means 162 from raising the hook 12 above alevel required for the engagement of the trough members 164 with theskid 18. Otherwise, the load beam 80 would be subject to bending byexcessive upward movement of the hook 12. Suitable protection can beprovided by a conventional limit stop means (not shown) that isoperatively connected to the winch means 162. With further reference toFIG. 9, a curve-shaped alternative configuration of the trough member164 permits a rocking motion between the trough member 164 and the skid18 for allowing the vehicle 10 to pitch relative to the cleaning module70.

Although the present invention has been described in considerable detailwith reference to certain preferred versions thereof, other versions arepossible. For example, the tank 82 can have a spherical shape, beingfabricated of a high-strength fibrous material such as carbon filamentfor providing improved payload capacity of the cleaning module 70 at agiven gross weight thereof. Also, the air switch 124 and/or the mediaswitch 129 can be operatively coupled to the cleaning module 70 by aradio link. Therefore, the spirit and scope of the appended claimsshould not necessarily be limited to the description of the preferredversions thereof.

What is claimed is:
 1. An apparatus for controllably suspending a load having a pair of spaced apart load connection points from a hoverable vehicle, the vehicle having a load attachment point, a releasable hook being connected thereto, and a pair of structural members fixably located on opposite sides of the attachment point, the apparatus comprising:(a) a rigid stabilizer bar having an attachment member for attachment to the attachment point and extending on opposite sides of the attachment point to respective first and second bar attachment points; (b) a yoke member having a hook attachment member for attachment to the releasable hook, the yoke fixably engaging the stabilizer bar when the hook attachment member is attached to the hook; (c) a pair of flexible load tension members, each of the load tension members being connected at one end thereof to a respective end of the yoke member; (d) means for connecting the other end of each load tension member to a respective load attachment point; and (e) biasing means for yieldably holding the stabilizer bar fixed about a vertical axis and at least one horizontal axis of the vehicle,whereby, when the hook is released, the yoke, together with the lines and the load, is jettisoned from the vehicle.
 2. The apparatus of claim 1 wherein the structural members are located on opposite sides of a longitudinal axis of the vehicle and the horizontal axis about which the biasing means yieldably holds the stabilizer bar corresponds to the longitudinal axis for coupling roll motion of the vehicle to the load.
 3. The apparatus of claim 1 wherein the structural members comprise a pair of landing gear members of the vehicle, and the apparatus further comprises means for defining an anchor point on each landing gear member, the biasing means connecting the bar attachment points to the anchor points.
 4. The apparatus of claim 3 wherein the biasing means comprises a pair of elastically extendable members each of the extendable members extending from proximate one of the bar attachment points to proximate a respective anchor point.
 5. The apparatus of claim 2 wherein the biasing means produces a first stiffness of the stabilizer bar about the longitudinal axis and a second stiffness about a lateral axis, the first stiffness being greater than the second stiffness.
 6. The apparatus of claim 5 wherein the first stiffness is at least about ten times that of the second stiffness.
 7. The apparatus of claim 6 wherein the first stiffness is between about ten and about fifty times that of the second stiffness.
 8. The apparatus of claim 4 wherein the anchor points are spaced apart horizontally, the bar attachment points being located in a vertical plane that intersects the anchor points.
 9. The apparatus of claim 8 wherein the bar attachment points define a bar axis, the bar axis proximately intersecting the attachment member.
 10. The apparatus of claim 9 wherein the bar axis is located vertically above the anchor points.
 11. The apparatus of claim 9 wherein the extendable members extend downwardly and outwardly from the bar attachment points.
 12. The apparatus of claim 11 wherein each extendable member comprises a bungee cord.
 13. The apparatus of claim 3, comprising means for defining a spaced pair of the anchor points on each landing gear member, the anchor points of each pair being spaced on opposite sides of a vertical plane that intersects the bar attachment points, the biasing means comprising pairs of elastically extendable members, each of the pairs of extendable members extending between one of the bar attachment points to proximate each anchor point of one of the spaced pairs of anchor points.
 14. A method for controllably suspending a load from a hoverable vehicle, the vehicle having a load attachment point, and a pair of structural members fixably located on opposite sides of the attachment point, the method comprising the steps of:(a) connecting a rigid stabilizer bar to the attachment point, the stabilizer bar extending on opposite sides of the attachment point to respective first and second bar attachment points; (b) biasingly connecting the first and second bar attachment points respectively to the structural members; (c) releasably connecting a yoke member to the load attachment point, the yoke member fixably engaging the stabilizer bar; (d) connecting a pair of flexible tension members at one end thereof to opposite ends of the yoke member; and (e) connecting the opposite ends of the tension members to respective spaced apart locations on the load. 